1. Field of the Invention
The present invention relates to a cooling device for a high voltage electrical unit for a motor of a vehicle, which is provided for cooling the high voltage electrical unit (including an electrical energy storing device, an inverter, etc.) installed in a vehicle which is solely driven by a motor, or in a vehicle which is driven by an engine and a motor. The present invention also relates to a hybrid vehicle having the cooling device for a high voltage electrical unit for a motor of a vehicle.
Priority is claimed on Japanese Patent Applications Nos. 2003-395283, filed Nov. 26, 2003, and 2004-145239, filed May 14, 2004, the contents of which are incorporated herein by reference.
2. Description of Related Art
In a vehicle which is solely driven by a motor, or in a vehicle which is driven by an engine and a motor (hereinafter referred to as a hybrid vehicle), when electrical energy is supplied from a battery, which is a direct current power source, to a motor thereof, the direct current is converted into alternating current by an inverter. In the case of a hybrid vehicle, a portion of output power of the engine, or a portion of the kinetic energy of the vehicle, is charged, via the motor, into the battery after converting alternating current into direct current by an inverter.
A battery and an inverter (hereinafter, a high voltage power source including a battery and an inverter, and a high voltage electrical device are, in general, referred to as a high voltage electrical unit) emit heat during operations thereof. The charging and discharging efficiency of a battery may decrease due to high temperature. An inverter has a permissible high temperature, and the inverter may be damaged when the temperature thereof exceeds the permissible high temperature. By increasing the capacity of an inverter, the amount of heat emitted from the inverter can be reduced; however, increase in the capacity results in increase in the size and weight of the inverter, which is not preferable in view of installation of the inverter in a vehicle because it is required for an inverter, which is to be installed in a vehicle, to be as small as possible. Accordingly, an inverter must be cooled.
As explained above, for a vehicle including such a high voltage electrical unit, it has been an important object how to efficiently cool the high voltage electrical unit within a limited installation space, and various attempts have been made to achieve such an object (see, for example, Japanese Unexamined Patent Application, First Publications Nos. 2003-79003 and 2001-233064).
However, in the technology disclosed in Japanese Unexamined Patent Application, First Publication No. 2003-79003, because a high voltage electrical unit is installed behind a rear seat, problems are encountered in that the rear seat cannot be folded, the size of a luggage compartment is limited, a point at which the high voltage electrical unit is connected to a structural body part is located far, long lines from a motor are required, a countermeasure for a rear impact must be considered, etc.
Moreover, in the technology disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-233064, because a high voltage electrical device and a high voltage power source are separately disposed, a problem is encountered in that two cooling systems are required.
Furthermore, when a high voltage power source is installed under a floor, as another technology other than those disclosed in Japanese Unexamined Patent Application, First Publication Nos. 2003-79003 and 2001-233064, problems are encountered in that upper surfaces of seats are located at a high position in order to ensure a minimum ground clearance, the passenger may feel that there is a lack of head clearance and uneasiness in getting in and out, a perfect sealing structure with respect to the passenger compartment must be considered, protection against heat of the exhaust system must be considered in the case of a hybrid vehicle, etc.
As explained above, a vehicle provided with a high voltage electrical unit may have degraded utility because the size of the vehicle cannot be significantly increased when compared with an ordinal gasoline vehicle.